The present application is directed to resonant inverter circuits, and more particularly to a voltage fed resonant inverter which operates continuously, from an open circuit condition at the output terminals to a short circuit condition.
Existing inverters include open- or short-circuit protection circuitry. One particular type of protection is through the use of pulse shutdown operations. In these designs, either the output voltage and/or the current that flows through resonant components or semiconductor switches is sensed to assist in the shutdown. When an open circuit situation occurs, such as when a lamp reaches its end-of-life, the maximum inverter current is detected, and the inverter is disabled or shut down before the components are overstressed. The use of the pulse shutdown technique will, however, cause an undesirable discontinuity of the output voltage. To accommodate new lamps which may not have recycling power, the inverter may also be periodically restarted. This periodic restarting results in an undesirable flicker as the lamp reaches its end of useful life. Voltage inverters which find particular benefit to protection in short circuit and/or open circuit situations are those being used in conjunction with discharge lamps including but not limited to linear fluorescent lamps (LFL), compact fluorescent lamps (CFL), and high intensity discharge lamps (HID).